May 1973 yielded figures of 5.85 and 1.97 per 100 

 m^, respectively. 



Recruitment was not noticeably high during 

 any particular quarter. However, medium-sized 

 shrimp in the 10- to 14-mm CL range were 

 significantly more abundant during the fourth 

 quarter (October-December) than at other times 

 of the year (Kolmogorov-Smirnov test, P<0.05). 



Diet (Table 5) 



Calanoid copepods made up the bulk of the 

 stomach contents of the S. erectus from DSB III. A 

 few amphipods and a single euphausiid were also 

 found. One individual had some material very 

 tentatively identified as a small fish, the only one 

 found in the DSB III collection. No food items in 

 the 0.4- to 0.6-mm size range were found. 



Sergestes armatus KrtSyer 1855 



Vertical Distribution (Figure 5) 



The daytime vertical distribution of 5. armatus 

 varied somewhat with size. Immature shrimp 

 ranged between 450 and 600 m; adults were gener- 

 ally between 550 and 650 m, but sometimes as 

 shallow as 450 m. One tow in November 1972 took 

 13 shrimp at about 675 m. The December 1970 



10 



\2 



1>4 



16 



10 



20 



200 



100 



600 



800 

 1000 

 1200 • 



200 

 400 

 600 

 800 

 1000 

 1200 



200 

 400 

 600 

 800 

 1000 

 1200 



DfiT 



NIGHT 



200 

 MOO 

 600 

 800 

 1000 

 1200 



200 

 400 

 600 

 800 

 1000 

 1200 



200 

 400 

 600 

 800 

 1000 

 1200 



6 8 10 12 

 CflfifiPfiCE LENGTH IMM) 



14 



16 



10 20 

 NO. PER 10^ m3 



Figure 5.- Vertical distribution of Sergestes armatus. 



FISHERY BULLETIN: VOL. 74, NO. 4 



cruise took nine shrimp in open tows below 800 m; 

 most of these were probably contaminants. The 

 nighttime range also varied with size; shrimp 

 smaller than 8 mm CL usually occurred between 

 100 and 200 m, while adults were found mostly 

 between 150 and 300 m, with occasional captures 

 as deep as 450 m. Moonlight did not depress the 

 vertical distribution of 5. armatus. The peak in the 

 upper 25 m is a sampling artifact. The open tows of 

 the December 1970 and December 1973 cruises 

 took small to moderate numbers of S. armatus at 

 the daytime depth. If these shrimp were not 

 contaminants, they suggest that about 5-20% of 

 the December 1973 population was not migrating. 



Population Size, Growth, and Reproduction (Figure 6) 



Sergetes armatus was abundant in the horizon- 

 tal series, the average population density of 2.35 

 per 100 m'-' estimated from all horizontal tows 

 making it the fourth most abundant sergestid. 

 The catch was even greater during the September 



1972 oblique series, which yielded a figure of 10.22 

 per 100 m'-\ second only to S. pectinatus. The May 



1973 oblique series took much smaller numbers, 

 amounting to only 1.51 per 100 m^'. 



Recruitment was much higher during the second 

 quarter (April-June) than during the rest of the 

 year. Large individuals were most abundant dur- 

 ing the fourth quarter (October-December). 



SERGESTES ARMATUS 



d 



9 



- jAN-MAR 



..^A 



-t JAN -MAR 



"T T "'I 1 r 



,.4^-n 



Pu-'Jk 



^^ 



q[\-nArin/x^ 



[1 



J 



/I 



T 1  — t 



14 2 



CARAPACE LENGTH (mm) 



ja» 



V 



10 



Figure 6.-Quarterly size-frequency distribution of Sergestes 



armatus. 



810 



